Bit



S. A. STOKES Filed NOV. 29, 1946 F/Gl IN V EN TOR. STANLEY ARCHER STOKES W9 an? 1 [TORNEYS Patented Aug. 5, 1947 BIT Stanley Archer Stokes, Pasadena, Calif.

Application Nilvember 29, 1946, Serial N0. 712,770

16 Claims.

This invention is concerned with drill bits and provides improved drill bits of novel design, particularly applicable to the drilling'of holes in concrete, stone'and similar hard, abrasive materials.

It has been proposed heretofore to employ bits faced with hard metal and cemented carbides for drilling concrete, stone etc. However, especially for core drills, the cemented carbides have proved much less satisfactory than diamonds.

As a result of my investigations, I have developed a'bit structure which increases the drilling efficiency of grinding media and permits cemented carbides and the like to be employed in many cases and in core-type drills with substantially all of the advantages 'of more expensive media such as diamonds.

The drill bit of my invention is designed to operate by grinding action as distinguished from a cutting action and in essence comprises "a drill head of erodable material rigidly mounted on a shank and eccentric with respect thereto. The drill head is disc shaped andm'ay be either circular or non-circular, 1. e, in its section transverse to the axis of rotation of the shank, and has at least three grinding teeth set approximately radially in its face, the outer'ends of "the teeth being spaced differently from the axis and substantially flush with the side of the 'head.

When the drill is rotated, the head wobbles slightly in the hole it makes, so that the grinding teeth exert both a rotary and'a sidewi'se abrading action.

Preferably the face of the head has an annular recess or core barrel located slightly eccentric with the axis of rotation of the shank. The core around which the teeth grind may be saved, or if preferred, broken out as drilling proceeds and ground out with the rest of the rock or concrete.

If desired, for-example, when the drill is to be employed to cut and conserve a core, the core barrel or hole in the face is concentric with the axis of the shaft. However, in many cases it is desirable to employ the bit while breaking up and removing the core. In such cases at least one of the grinding members should be permitted to project slightly into the core barrel 'so that it provides a "break out to aid in chewing up the core. Moreover in such cases it is desirable that the core barrel or recess be slightly off center of the axis of the shank, and of non=circularcross section to correspond with-the outside of the head.

Immediately above the bit proper, the apparatus should be provided with an exterior screw thread or auger to remove cuttings from the neighborhood of the grinding face.

The face of the drill head should be flat and perpendicular to the axis, and the several grinding members should project from it in differing amounts. Thus the first grinding member or tooth may project a small amount, the second slightly more and the third still more.

I prefer to employ teeth which are roughly parallelepipeds and to set them at an angle with the face of the bit, this angle being obtuse having in mind the direction of rotation of the bit.

For best results, the exposed long edge of the tooth should be set parallel to a radius drawn from the axis of rotation but slightly in advance of this radius in the direction of rotation of the bit. Bits so constructed operate more easily and do not tend to stick in the hole, perhaps because sucha setting tends to make the front of the side edge of the tooth project slightly beyond the path of the rear of the tooth, assuming that the side edge is perpendicular to the exposed long edge, as will be apparent from a study of the following detailed description taken in conjunction with the accompanying drawings in which Fig. 1 is a plan view of one form of my bit particularly adapted to cutting a core;

Fig. 2 is an elevation of the bit of Fig. 1;

Fig. 3 is a plan View of a bit of my invention adapted for drilling holes and simultaneously breaking up thecore, and

Fig. 4 is an elevation of the bit of Fig. 3.

I Referring to Figs. 1 and 2, the bit comprises a head Ill formed integrally on a cylindrical shank portion H which is rotatable around an axis I2. The face of the head is flat and perpendicular to the axis and is provided with a cylindrical recess or core barrel 13, the axis I2A of which is eccentrio with the axis 1'2. This recess may be of any desired depth and in some cases may run entirely through the shank and its extension IIA.

Set in the face of the head are three radial grinding teeth 14, I5 and it. The inner edges of all three grinding members are spaced equidistant from the axis and substantially flush with the wall of the core barrel. As shown in Fig. 1, the preferred direction of rotation of the bit is counterclockwise. The first tooth I4 is relatively short in a radial direction, the next tooth l5 being longer (say by /128 inch) and the tooth l6 being still longer (say by /64 inch). All extend approximately radially. The'head is so shaped that its Wall is substantially flush with the several ends of the cutting members, giving a noncircular form to the face. Thus the head is in the shape of a disc of eccentric external circumference.

All three of the grinding members are set in the face at an angle which may be clearly seen in Fig. 2 in the case of the grinding member l6. Thus the grinding member l6 inclines backward so that it presents its angular outer edge at an obtuse angle (say 120) having in mind the direction of rotation of the bit.

The short tooth I4 projects farther from the face than 'does the somewhat longer tooth I5, and this in turn projects farther from the face than the longest tooth I 6,

In t app tus of Figs. 1 and 2, the shank I l is provided with an auger which is formed by means of an helical spring I! wound tightly around the shank. The upper end of the spring has a tit l 8 which is bent downwardly to ride in a longitudinal groove l9.

It will be observed that the outside of the spring coil corresponds in cross section approximately to that of the head, save that it is wound on a true cylinder concentric with the axis. The helical spring and its attendant groove l9 are useful in that the spring may be unclipped and slid off the shank for easy cleaning.

The drill of the invention makes holes so much faster than conventional types that the auger is essential for fast operation, i. e., to remove grindings as fast as they are formed.

The shank may be of any convenient length with its extension I IA shaped to fit a convenient chuck.

In using the apparatus of Figs. 1 and 2 for drilling holes in concrete, the drill is simply fasteiied in the chuck of a rotatable spindle, say that of a portable electric drill, and the face of the drill is held against the concrete. Manual pressure is sufficient to permit the rotating face to cut rapidly into the concrete, this cutting action being in reality a grinding action in which the rotary action of the teeth is aided by a slight wobbling action of the face, brought about by the fact that the outer ends of the teeth are eccentric with respect to the axis of rotation of the drill and substantially flush with the side of the head. In order to accomplish this condition the head may be either circula in transverse section and mounted on the shank eccentrically to the axis of rotation thereof, or non-circular in transverse section and mounted to the shank either concentrically or eccentrically to its axisof rotation. In either case the head induces the wobbling action within the hole. Despite the wobbling action, it has been found that a core will be left without breaking, should the core barrel be drilled concentric to the axis of the shank.

Figs. 3 and 4 illustrate another variety of drill particularly adapted for breaking up and removing a core during the hole-grinding operation. As in the previous case, the apparatus comprises a head 30 having a shank 3| in the form of an anger. The face of the head is perpendicular to the axis of rotation 32 of the shank and there is a core barrel or annular recess 33 in the cutting face. This recess has straight sides parallel to the axis of rotation. The face of the head is provided with three teeth 34, 35, 36. All are disposed approximately radially with respect to'the axis and set in the face. Considering that the direction of rotation of the drill is counterclockwise as viewed in Fig. 3, the first tooth 34 is shortest. The second tooth 35 is somewhat longer and also has its inner end spaced at. a slightly greater distance from the axis of rotation than the inner end of the first tooth. The last tooth 36 is the longest. Its outer end is spaced farther from the axis than the outer end of the tooth 35. However, it is provided with an extension on the inner end which rel is shaped similarly and the core barrel is likewise eccentric with respect to the axis.

The teeth of the drill of Figs. 3 and 4 are set slantwise in the face as in the case of the teeth in the apparatus of Figs. 1 and 2, and likewise the 1 several teeth of the apparatus of Figs. 3 and 4 project in differing amounts from the face of the bit.

The auger stem (Fig. 4) serves the purpose of the helical spring shown in Fig. 2.

The operation of the apparatus of Figs. 3 and 4 is the same as that of Figs. 1 and 2, save that the core, due to the unsymmetrical shape of the core barrel and the presence of the break out or extension of the tooth 36 within the core barrel, is

broken up and ground away with the rest of the rock in the path of the bit.

The bits of my invention will operate satisfactorily at various speeds, and I have found that 2;. speeds ranging from 400 to as high as 2,500

R. P. M. are entirely practical.

It was noted previously that some improvement in operation can be obtained through careful setting of the teeth in the head, so that the long edge of each tooth, which bears the brunt of the grinding, is set parallel to but slightly in front of a radius drawn from the axis of rotation of the shank. This is illustrated particularly in the case of the tooth 34 in Fig. 3. Its exposed long edge T34A is parallel to the radius 343 but leads it slightly in the direction of rotation (counterclockwise as viewed in Fig. 3). The outside end 340 of the tooth is substantially perpendicular to the edge 34A, with the result that its front portion projects from the axis by a slightly greater 40 amount than the trailing portion.

The other teeth in both drills illustrated are similarly set in the face.

Whether or not the immediately foregoing paragraph is followed in setting the teeth, the

leading outside portion of each tooth should project by a slightly greater amount than the trailing portion of that tooth. Otherwise the trailing portion is unduly burdened.

The screw thread or auger of the device is cssential for proper dry operation at high speeds,

since otherwise the bit makes hole so fast that the cuttings or grindings cannot be properly removed.

The teeth may be set at various angles with respect to the face, although as shown in Figs. 2

and 4, an obtuse angle of approximately 120 degrees is about optimum.

The shank preferably is made of a good grade of tooth steel, and the teeth may be set therein by various methods, including brazing or with silver solder. However, I prefer to set the teeth by a low temperature welding operation employing a welding alloy having a melting temperature of about 900 F., but so constituted that upon 5 re-melting some of its alloy ingredients tend to volatilize leaving a residue with a melting point of about 1600 F.

Any cemented carbides that are particularly abrasion resistant may be employed as grinding members and cutting members such as diamonds embedded, so that use of more expensive grinding media such as diamonds *is not econom-lca-lly justi fied.

I attribute the-high efficiency-of the drill bit of my invention tb the smooth wehbling efreet wrath aids {the rotary -grinding action which comes about by using teeth whose outer ends are disposed eccentrically to the axis of rotation of t-he drill, the smooth eccentric action being assured by the eccentric cross section of thedr ill face. By making the teeth project different distances, ho'le making efficiency is substantially improved.

The device must have at least three teeth; otherwise it is difficult 'to drill straight holes, especially in material such as concrete where pieces of different hardness are encountered.

The drill in its preferred form is self cleaning and requires no liquid or other fluid for flushing grindings away from the face.

Iclaim:

1. In a drill bit the combination comprising a rotatable shank, a disc-shaped head 'of eccentric external circumference mounted on one end of the shank eccentrically to the axis of rotation thereof, and at least 3 teeth set approximately radially in the face of the head and perpendicular to the axis of rotation of the shank, the outer ends of each of the teeth being flush with the side wall of the head, the head being free to Wobble slightly in a hole being drilled, whereby the teeth exert both a rotary and lateral grinding action in the hole.

'2. Ina drill bit the combination comprising 73, rotatable shank, a disc-shaped head of eccentric external circumference mounted on one end of the shank eccentrically to the axis of rotation thereof, a circular recess in the face of the head, said recess being eccentric to the axis of rotation of the shank, and at least three teeth set approximately radially in the face of the head and perpendicular to the axis of rotation of the shank, the outer ends of each of the teeth being substantially flush with the side wall of the head.

3. In a drill bit the combination comprising a rotatable shank, a disc-shaped head of eccentric external circumference mounted at one end of the shank eccentrically to the axis of rotation thereof, at least three teeth set approximately radially in the face of the head and perpendicular to the axis of rotation of the shank, the outer ends of the teeth being spaced differently from the axis and substantially flush with the side Wall of the head, the head being free to wobble slightly in a hole being drilled, whereby the teeth exert both a rotary and lateral grinding action in the hole.

4. In a drill bit the combination comprising a rotatable shank, having an exterior screw thread, a disc-shaped head of eccentric external circumference mounted at one end of the shank eccentrically to the axis of rotation thereof, and at least three teeth set approximatel radially in the face of the head and perpendicular to the axis of rotation of the shank, the outer ends of each of the teeth being flush with the side Wall of the head, the head being free to wobble slightly in a hole being drilled, whereby the teeth exert both a rotary and lateral grinding action in the hole.

5. In a drill bit the combination which comprises a metal head mounted on a rotatable shaft and having an exposed face transverse to the axis of rotation of the shaft, at least three grinding teeth set in the face and extending transverse to the axis, the outer ends of the several teeth being set at different distances from the axis and substantially flush with the side of the head, the

6 headbe'ing freeto wobble slightlya'n "a hole being drilled, whereby the teeth exert both a rotary and lateral g rinding action in the hole.

6. In a drill bit the combination which comprises a metal head mounted on a rotatable shaft and having an eccentric face transverse to the axis of rotation of the shaft, at least three grind ing "teeth set in the face and extending transverse to'the axis, the outer ends of the several teeth being set at different distances from the axis and substantially flush with the side of the head and the several teeth projecting different distances from the face of the head, the 'head being free to wobble slightly in a hole being drilled, whereby the teeth exert both a rotary and lateral grinding action in the hole.

7. In 'a drill bit the combination which comprises 'a metal head mounted on a rotatable shaft and having an eccentric face transverse to the axis of rotation of the shaft, at least three grinding teeth set in the face and extending transverse to the axis, the outer ends of the several teeth being set at progressively greater distances from the axis'and substantially flush with the side of the head, the head being free to wobble slightly in a hole being drilled, whereby the teeth exert both a rotary and lateral grinding action in the hole.

'8. An apparatus according to claim '7 in which the teeth are set out progressively farther from the face of the head.

9. In a drill bit a combination which comprises a metal head mounted on a rotatable shaft, the head having an annular face transverse to the axis of rotation of the shaft, at least three grinding teeth set in the face and extending transverse to the axis, the outer and inner ends of the several teeth being set at different distances from the axis with the outer ends substantially flush with the side of the head, the head being free to wobble slightly in a hole being drilled, whereby the teeth exert both a rotary and lateral grinding action in the hole.

10. In a drill bit the combination which comprises a metal head mounted on a rotatable shaft and having an eccentric face transverse to the axis of rotation of the shaft, a plurality of grinding teeth set in the face at an angle oblique thereto and extending transverse to the axis, the outer ends of the several teeth being set at different ditsances from the axis and substantially flush with the side of the head, the head being free to wobble slightly in a hole being drilled, whereby the teeth exert both a rotary and lateral grinding action in the hole.

11. In a drill bit the combination which comprises a rotatable shaft, a metal head mounted on the shaft and having an eccentric annular face transverse to the axis of rotation of the shaft and of eccentric inner circumference, a plurality of grinding teeth set in the face and extending substantially radially transverse to the axis, the outer ends of the several teeth being set at different distances from the axis and substantially flush with the side of the head, with the inner end of at least one tooth extending towards the axis from the annular face.

12. In a drill bit the combination which comprises a metal head mounted on a rotatable shaft and having an annular face transverse to the axis of rotation of the shaft a plurality of grinding teeth set in the face and extending transverse to the axis, the outer ends of the several teeth being set at different distances from the axis and substantially flush with the side of the head, with the inner' ends of the respective teeth similarly spaced with respect to the axis, and the inner end of at least one tooth extending into the annular space within the head, the head being free to wobble slightly in a hole being drilled, whereby the teeth exert both a rotary and lateral grinding action in the hole, 7

13. An apparatus according to claim 12 in which some of the teeth project further from the face of the head than do others.

14. In a drill bit the combination which comprises a metal head mounted on a rotatable shaft and having an eccentric face transverse to the axis of rotation of the shaft, a plurality of grind ing teeth of abrasion esistant cemented tungsten carbide composition set in the face and extending transverse to the axis, the outer ends of the several teeth being set at different distances from the axis and substantially flush with the side of the head, the head being free to wobble slightly in a hole being drilled, whereby the teeth exert both a rotary and lateral grinding action in the hole.

15. In a drill bit the combination comprising a rotatable shaft, a disc-shaped head of eccentric external circumference mounted at one end of the shaft, said head having a face transverse to the axis of rotation of the shaft, a plurality of grinding teeth of abrasion resistant cemented tungsten carbide composition extending transverse to the axis, the outer ends of the several teeth being set at different distances from the axis and substantially flush with the side of the head, the head being free to wobble slightly in a hole being 8 drilled, whereby the teeth exert both a rotary and lateral grinding action in the hole.

16. In a drill bit the combination comprising a rotatable shaft having an exterior screw thread, a disc-shaped head of eccentric external circumference mounted at one end of the shaft having a face transverse to the axis of rotation of the shaft, a plurality of grinding teeth set in the face and extending transverse to the axis, the outer ends of the several teeth being set at different distances from the axis and substantially flush with the side of the head, the head being free to wobble slightly in a hole being drilled, whereby the teeth exert both a rotary and lateral grinding action in the hole.

STANLEY ARCHER STOKES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,020,625 Thaheld Nov. 12, 1935 2,300,805 Pew Nov. 3, 1942 1,271,396 Walker July 2, 1918 1,862,814 Wright et a1 June 14, 1932 710,484 Mackenzie Oct. '7, 1902 1,852,843 Greve Apr. 5, 1932 443,072 Chapman Dec. 16, 1890 1,885,085 Dalzen 'Oct, 25, 1932 1,733,241 Scott Oct. 29, 1929 1,887,372 Emmons Nov. 8, 1932 

